butler



1 NITED STATES PATE MATTHEW w. BUTLER, or CLEVELAND, oHro, ASSIGNOR'TO THE HARSI-IAW, FULLER & eoonwnv COMPANY, or cLEvELANnoHro, A CORPORATION or 01110.

METHOD OF MAKING LEAD ARSENATE.

No Drawing.

To all whom it may colic-em.-

Be it known that I, MATTHEW W. BUTLER, a citizen of the United States, and a resident of Cleveland, county of Cuyahoga, and State 5 of Ohio, have invented a new and useful Improvement in Methods of Making Lead Arsenate, of which the following is a specification, the principle of the invention being herein explained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

A well known and generally practised method of making sodium nitrite (NaNO is by heating sodium nitrate (NaNO with metallic lead. In addition to the desired nitrite, there results from this process a lead compound by-product. The exactconstitution of this by-product apparently varies, although it seems to consist mainly of lead oXid in one form or another; at least it has been found that by heating such product for a considerable length of time, under proper conditions, red lead is' formed, while it is claimed that by shorter heat treatment, under different conditions, a fine quality of litharge results.

The product itself, however, as it comes from the main process, is not marketable, and the present invention accordingly has as one of its objects the utilization, in a practical and profitable way, of what is otherwise a more or less waste product, from the manufacturing standpoint. The present invention is based on the discovery that this lead compound by-product, whatever its constitution, readily reacts with arsenic acid in solution to produce a high grade lead arsenate; that is, a lead arsenate having a good color and of a diffuse or flocculent character, adapting itfor use as an insecticide, either in powder or paste form. I

The steps involved in carrying out my improved process will now be fully described and particularly pointed out in the claims, the following description, however, setting forth in detail but one of various modes of carrying out the invention, or ways in which the principle of such invention may be used. The reaction that occurs when sodium nitrate is heated with metallic lead, may be represented by the following equation:

' in which the by-product is indicated as lead Specification of Letters Patent.

. nitrate and metallic lead together.

Patented Dec. 9, 1919.

Application filed December 8, 1917. Serial No. 206,271.

monoxid. It is not essential, however, to the present process to inquire into the exact character of this reaction, nor to make certain that the by-product in question is composed of this particular oxid. Neither is it material whether this oxid, if present, be in the yellow form known as massicot, or in the reddish form known as litharge.

In making sodium nitrite in the fashion just described, the resulting mass is lixivi- 'ated so as to dissolve and wash out the nitrite, leaving lead compound by-product behind. The latter is then filtered ofi, in a suitable filter press, being subjected to one or more intermediate washings if desired, in order to thoroughly extract the nitrite, with the result that a grayish or dirty yellow cake is obtained. This cake, which is readily friable, is then broken up and mixed with water, in which the particles remain more or less in suspension.

To the mixture thus obtained is then added an amount of arsenic acid proportionate to the amount of lead determined to be present, or, if desired, the original solution, to which the by-produ'ct is thus added, may contain the proper quota of arsenic acid.

Such arsenic acid, whatever the manner of its addition to the mixture, is found to react promptly with the lead compound. This reaction, assuming the compound to be the monoxid, will be in accordance with the i following equation:

The resulting arsenate precipitates out, and may be separated by filtration in any approved way. As previously indicated, it is in very satisfactory form for use as an insecticide, possesses a good color, and is adapted for use either after dryin as a powder, or directly as it comes from t e reaction as a paste. My improved process, thus not only produces a highly satisfactory commer-' cial product having a ready market, but utilizes a by-product which has heretofore always been regarded as a hampering factor in the commercial ractice of the process for making sodium nltrite by heating sodium Other modes of applying the principle of my invention may be employed instead of the one explained, .change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent 'of such stated step or steps be employed.

I therefore particularly point out and distinctly claim as my invent1on:-

1. The method of making lead arsenate,

which consists in reacting with arsenic acid upon the lead compound by-product of the making of sodium nitrite by heating sodium nitrate and metallic lead.

2. The method of making lead arsenate, which consists in filtering off the lead compound by-product of the making of sodium nitrite by heating sodium nitrate and metallic lead, and mixing such compound with a solution of arsenic acid.

3. The method of making lead arsenate, which consists in filtering oi the lead compound by-product of the making of sodium nitrite by heating sodium nitrate and metallic lead, and mixing such compound with 20 a solution of arsenic acid, the amount of arsenic acid being proportioned to the amount of lead in such compound. 4

Signed by me, this 5th day of December,

MATTHEW W. BUTLER. 

